FIG. 1 schematically illustrates a guided air-to-air missile 10. In operation, a sensing system 12 positioned in the nosecone of the missile 10 continually produces electrical signals that indicate the position of a targeted air vehicle. These signals are communicated along lines 14 to an electronic control system 16 ("ECS"), wherein they are processed to produce electronic control signals 18. The control signals 18 are communicated to coils 20 (FIG. 5) which form the electrical components of a plurality of electrofluidic interfaces 22. The fluidic interfaces 22 govern the flow of nitrogen gas from a pressurized container (not shown) thereof to a plurality of fin actuators 24 in accordance with the magnitudes and polarities of the control signals 18. The fin actuators 24 position four control surfaces (as at 26) to direct the missile 10 to the targeted vehicle.
The fluidic interfaces 22 are typically provided in the form of electrofluidic pin transducers, the fluidic operation of which can be generally understood by reference to FIG. 4. A fluidic circuit element 28 (illustrated by dashed lines) is formed by a laminate subassembly 29, and comprises a supply port 30 and two receiving channels 32, 34. Both receiving channels 32,34 are in fluid communication with a fin actuator 24 (FIG. 1). Fluid is delivered from the pressurized container to the supply port 30. Flow proceeds generally in the direction of a flow path which extends from the center of a nozzle 35 to the center of a flow splitter 36 which is positioned between the receiving channels 32,34. This direction is generally indicated by the x-axis of a directional reference 37 provided in FIG. 4. If either of the receiving channels 32,34 receives more fluid than the other, there is a resulting bias in the fluidic output signals delivered from the receiving channels that can be used by the fin actuator 24 to move the control surface 26.
A boss 38 extending from a flexible beryllium-copper member 40 (FIG. 5A) has two flow windows 42,44 formed therethrough, the windows being separated by a pin 46. The pin 46 is positioned in the flow path just upstream from the flow splitter 36, as indicated by FIG. 3A. By moving the pin 46 in either of the rotational directions indicated in FIG. 3A by the curved arrow 48, fluid flow can be split between the receiving channels 32,34 as necessary to provide the appropriate bias in the forementioned fluidic output signals.
Viewing FIG. 3, movement of the pin 46 is typically accomplished via an electromagnetic subassembly 50 of the pin transducer. The subassembly 50 comprises a magnet 52, a coil 20, first and second pole pieces 54,56, and the forementioned flexible member 40. A control signal 18 (FIG. 1) communicated to the coil 20 produces an electromagnetic field that interacts with the magnetic field continuously produced by the magnet 52. This field interaction causes the coil 20 to rotate to a degree and in a direction dependent upon the magnitude and polarity, respectively, of the control signal 18. The coil 20 is seated on a flange 58 of the flexible member 40, and the boss 38 is substantially immovable relative to the flange 58. Accordingly, as the coil 20 rotates in either of the directions indicated by the arrow 48, so does the pin 46.
In the manufacture of an electrofluidic pin transducer of the type generally described above, it is important to ensure that the null position of the pin 46 does not drift. The null position is a preset position at which no differential fluidic output is observed for the receiving channels 32,34. The transducer, once assembled, must be subjected to a series of tests to determine whether the null position will hold when the transducer is subjected to various environmental hazards such as vibration and thermal stress.
FIG. 2 schematically illustrates the manner in which adjustment of the null position has been accomplished prior to the present invention. The flexible member 40 in the prior art defines two leaf springs (as at 60) that extend into the fluidic subassembly 29. The leaf springs 60 may be formed, for example, by appropriately cutting and bending portions of the flange 58. Each of these springs 60 rests on the end of a set screw (as at 62) which is disposed in the fluidic subassembly 29. Adjustment of the null position is effected by driving the set screws 62 as needed to position the pin 46 (FIG. 3A). Under that arrangement, movement of the pin 46 for null setting purposes occurs in the same directions 48 (FIG. 3A) as movement for control purposes. Since the null position may be set at various positional combinations of the set screws 62 and thus various tensions of the leaf springs 60, sensitivity to a given magnitude of control signal 18 may vary from interface 22 to interface. Moreover, surface-to-surface contact between the ends of the leaf springs 60 and the ends of the set screws 62 is not a well-defined parameter. If this contact changes due to mechanical shock or thermal stress, for example, the pin 46 may move away from the null position. If such movement happens at any time between shipment of the interface 22 and firing of the missile 10, the accuracy of the missile may be seriously impaired.
An objective of this invention is to provide an electrofluidic pin transducer that consistently maintains a preset null position.
A further objective is to provide such a transducer in which the null position is set by manual rotation of a single adjustment mechanism.
A still further objective is to improve precision and accuracy for guided air-to-air missiles which employ electrofluidic pin transducers as interfaces.